A couple additions:
Please don't say any of the following:
"I'm so stupid"
"I'm computer illiterate"
"You must hate talking to stupid people like me"
Unless you want a truthful answer. There's nothing I hate more than coddling your ego while I try to fix your computer problems.
Also, don't lie. Trust me, I'll figure it out pretty soon anyway, and it's just going to make it more painful for both of us.
Only call when you are at your computer, it is on, and you have enough time to talk. Calls on your cell phone from the car on your way to work are not likely to be productive.
And always remember this, once you call tech support you forfeit your rights to being the smart guy. If we tell you to do something, don't question it. In addition to this, don't tell us what your computer savvy friend thinks the problem is. He's probably an idiot and we frankly don't care.